Question

我有一个类FilePlay，它接受三个参数host_dic，PATH，group都具有默认值。当给出host_dic时，对象实例化将创建一个文件。当没有给出对象实例化时，将检查文件是否存在，如果不存在则会引发错误。这是代码：

class FilePlay(object):
    def __init__(self, host_dic=None, PATH='/foo/', group='bar'):
        self.host_dic = host_dic
        self.PATH = PATH
        self.group = group # this changes with the instantiation

        if isinstance(hosts_dic, dict):
            # create a file
            # change self.group
        else:
            if os.path.isfile(self.PATH+'hosts'):
                # read the file
                # change self.group
            else:
                raise IOError("Neither hosts file found nor host_dic parameter given, cannot instantiate.")

现在我想用unittest测试一下。所以这是我的代码：

import unittest
from top.files import FilePlay
import os.path  


class Test_FilePlay(unittest.TestCase):

def test_init_PATH(self):
    '''It tests FilePlay instatiation when:
       PATH parameter is given
    '''
    test_PATH='/foo/'

    if not os.path.isfile(test_PATH+'hosts'): # If there is no hosts file at PATH location
        self.assertRaises(IOError,play = FilePlay(PATH=test_PATH)) #Here is the problem!
    else: # if there is the hosts file at PATH location
        play = FilePlay(PATH=test_PATH)

        self.assertEqual(play.group, 'bar')
        self.assertEqual(play.hosts_dic, None)

当我尝试使用PATH位置的文件运行测试时，它可以正常工作。但是当文件不存在时，我得到：

======================================================================
ERROR: test_init_PATH (top.tests.test_test_file)
It tests FilePlay instatiation when:
----------------------------------------------------------------------
Traceback (most recent call last):
  File "top/tests/test_file.py", line 14, in test_init_PATH
    self.assertRaises(IOError,play = FilePlay(PATH=test_PATH))
  File "top/ansible_shared.py", line 88, in __init__
    raise IOError("Neither hosts file found nor host_dic parameter given, cannot instantiate.")
IOError: Neither hosts file found nor host_dic parameter given, cannot instantiate.

----------------------------------------------------------------------
Ran 1 test in 0.001s

FAILED (errors=1)

当文件不存在时，如何通过测试？

Answer 1

您未正确使用assertRaises。您直接调用该对象，以便在断言有机会捕获它之前引发错误。

您需要单独传递类本身及其参数：

self.assertRaises(IOError, FilePlay, PATH=test_PATH)

或使用上下文管理器版本：

with self.assertRaises(IOError):
    FilePlay(PATH=test_PATH)

将unittest assertRaise（）与对象实例化一起使用

1 个答案: